Structural and superconducting properties of PIT processed sintered MgB 2 /Fe wires S. Balamurugan a , T. Nakamura a, * , K. Osamura b ,I.Muta a , T. Hoshino a a Department of Electrical Engineering, Kyoto University, Kyoto-Daigaku Katsura 1, Nishikyo-ku, Kyoto 615-8510, Japan b Department of Materials Science and Engineering, Kyoto University, Yoshida-Honmachi, Sakyo-Ku, Kyoto 606-8501, Japan Received 29 October 2003; accepted 8 March 2004 Available online 24 June 2004 Abstract In this paper, we report the structural and superconducting properties of MgB 2 /Fe wires that are produced by different sintering conditions. Good quality MgB 2 /Fe wires are fabricated by the powder-in-tube (PIT) method using commerciallyavailableMgB 2 powderatambientpressure.Inordertochecktheannealingeffect,thedifferentpiecesof the as-rolledwiresaresinteredat1323Kfor0.30–1.20ks.XRDdataconfirmsthattheyarehexagonalMgB 2 structure. All the sintered samples show higher T c valuesintherangeof38.2–38.4Kwithhigh J c than the as-rolled sample. No significantchangein T c isseenamongtheannealedsamples.Ontheotherhand,theannealedsamplesshowsignificant changeinthe J c valuesaswellasinmicro-structuralfeaturesduetovariablesinteringtime.Onannealingat1323Kfor 0.60ks,weobtainthebestqualitysamplewitha J c of372A/mm 2 at33.1Kinself-fieldwithamaximum T c of38.4K. Among the annealed samples, 1.20 ks sample shows lower J c . Longer annealing time reduced J c , indicating a possible interfacial reaction between the Fe sheath and the MgB 2 core. Ó 2004 Elsevier B.V. All rights reserved. PACS: 85.25.K Keywords: Superconductivity; MgB 2 ; PIT; Sintering; Critical current density 1. Introduction The recent discovery of superconductivity in MgB 2 by Nagamatsu et al. [1] with the highest superconducting transition temperature (T c )of39 Khasstimulatedgreatinterestintheareaofboth fundamental research and practical applications [2]. In addition to impressive progress made for magnet and power applications [3], promising Josephson-junctions have also been successfully fabricated [4]. The simple chemical composition and simple crystal structure, relatively higher T c , absenceof weak-link nature,hightransportcritical currentdensity(J c )andlowcostofmaterialsmake MgB 2 a very attractive candidate for practical applications [2–8] in the temperature range 20–30 K to overcome the problem of low tempera- ture operation with conventional Nb-based * Corresponding author. Tel.: +81-75-383-2223; fax: +81-75- 383-2224. E-mail address: tk_naka@kuee.kyoto-u.ac.jp (T. Nakam- ura). 0921-4534/$ - see front matter Ó 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.physc.2004.05.001 www.elsevier.com/locate/physc Physica C 412–414 (2004) 1184–1188